There is increasing evidence that brain regions of autistic individuals have altered neural connectivity between different brain regions. Preliminary work has shown that autistic brains tend to have changes in the structure and anatomy of the white matter tracts that carry neural information between brain regions. The methods commonly used to visualize the anatomy of white matter, diffusion tensor magnetic resonance imaging (MRI) and diffusion-tensor tracking, do not provide a level of microscopic detail which would allow researchers to determine the underlying biological causes of the structural abnormalities observed in white matter. In the present study, Dr. Conturo and colleagues will develop new diffusion MRI techniques which will allow them to examine the microscopic structure of white matter tracts. They will combine existing diffusion MRI methods with novel computational approaches aimed at determining the cellular basis of white matter abnormalities, and apply these new methods to examining the brains of individuals with autism. This research may help to define the underlying cellular disturbances which result in abnormal white matter tracts in autism, as well as provide new diagnostic tools for neurodevelopmental disorders.